Northern Missouri
The county seat is Palmyra, not Hannibal
In Marion County, the larger city (Hannibal, on the Mississippi) is not the county seat. The seat is Palmyra, and the county also keeps a courthouse in Hannibal, so confirm where your office or court matter is handled.
Palmyra, not Hannibal, is the seat of Marion County. That can surprise people because Hannibal is larger and better known, with its place on the Mississippi River. The main courthouse and the county clerk’s office are in Palmyra, including the clerk listing at 100 S. Main.
Hannibal is still part of the county-government map. Marion County keeps a second courthouse there, and some county business may route to that building. The county seat answer is Palmyra; the errand answer may still depend on which office or court function you need.
So a tax payment, assessment question, property record, clerk request, or court matter should start with the office location, not the best-known city name. Hannibal and Palmyra both show up in Marion County civic life. Palmyra is the seat, and the second courthouse in Hannibal is the reason to read the routing before driving.
References
Where this fits: this note belongs to Marion County. See every local note for the county on its page.